Supplementary information from Earlier colony arrival but no trend in hatching timing in two congeneric seabirds ( Uria spp.) across the North Atlantic.

• Main Authors: Benjamin Merkel, Sébastien Descamps, Nigel G. Yoccoz, Jóhannis Danielsen, Francis Daunt, Kjell E. Erikstad, Aleksey V. Ezhov, David Grémillet, Maria Gavrilo, Svein-Håkon Lorentsen, Tone K. Reiertsen, Harald Steen, Geir H. Systad, Þorkell Lindberg Þórarinsson, Sarah Wanless, Hallvard Strøm
• Format: Other Non-Article Part of Journal/Newspaper
• Language: unknown
• Published: 2019
• Subjects: Ecology; Animal Behaviour; guillemots; murres; pre-laying period; timing of egg-laying; Uria aalge; Uria lomvia; North Atlantic; uria
• Online Access: https://doi.org/10.6084/m9.figshare.9948509.v2; https://figshare.com/articles/journal_contribution/Supplementary_information_from_Earlier_colony_arrival_but_no_trend_in_hatching_timing_in_two_congeneric_seabirds_i_Uria_i_spp_across_the_North_Atlantic/9948509

A global analysis recently showed that seabird breeding phenology (as the timing of egg-laying and hatching) does not, on average, respond to temperature changes or advance with time (Keogan et al. 2018 Nat. Clim. Change 8 , 313–318). This group, the most threatened of all birds, is therefore prone to spatio-temporal mismatches with their food resources. Yet, other aspects of the breeding phenology may also have a marked influence on breeding success, such as the arrival date of adults at the breeding site following winter migration. Here, we used a large tracking dataset of two congeneric seabirds breeding in 14 colonies across 18° latitudes, to show that arrival date at the colony was highly variable between colonies and species (ranging 80 days) and advanced 1.4 days/year while timing of egg-laying remained unchanged, resulting in an increasing pre-laying duration between 2009 and 2018. Thus, we demonstrate that potentially not all components of seabird breeding phenology are insensitive to changing environmental conditions.